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Table 1 Characteristics of the systematic reviews included in each overview

From: The impact of different inclusion decisions on the comprehensiveness and complexity of overviews of reviews of healthcare interventions

Overview topic and SR category Number of included SRs Years of publication of SRs, median (range)a AMSTAR score, mean (standard deviation) Total number of included primary studies Unique primary studies, n and % included in at least one SRb Primary study overlap between SRs (“CCA”)c
Overviews for which Cochrane SRs examined all relevant intervention comparisons
 Bronchiolitis 7 2009 (1996–2010) 8.1 (3.0) 55 29 High (14.9)
  Cochrane 4 2010 (2009–2010) 10.5 (0.6) 33 26 (90%)  
  Non-Cochrane 3 1997 (1996–2004) 5.0 (1.0) 22 13 (45%)  
 Croup 6 2008 (1989–2010) 8.3 (3.0) 69 53 Moderate (6.0)
  Cochrane 4 2010 (2006–2010) 9.5 (1.9) 51 50 (94%)  
  Non-Cochrane 2 1995 (1989–2000) 6.0 (4.2) 18 18 (34%)  
 Gastroenteritis 15 2007 (2001–2012) 7.7 (1.8) 228 114 High (13.3)
  Cochrane 3 2010 (2006–2010) 10.7 (0.6) 88 88 (77%)  
  Non-Cochrane 12 2007 (2001–2012) 6.9 (1.1) 140 82 (72%)  
Overviews for which Cochrane SRs did not examine all relevant intervention comparisons
 Acute asthma 13 2011 (1997–2013) 7.8 (2.0) 82 56 Slight (3.9)
  Cochrane 7 2011 (2002–2013) 8.4 (1.8) 48 45 (80%)  
  Non-Cochrane 6 2006 (1997–2013) 7.0 (2.0) 34 34 (61%)  
 Acute otitis media 15 2009 (1994–2011) 8.1 (2.6) 260 135 Moderate (6.6)
  Cochrane 6 2009 (2007–2011) 10.2 (0.8) 87 84 (62%)  
  Non-Cochrane 9 2006 (1994–2010) 6.7 (2.5) 173 107 (79%)  
 Eczema 19 2007 (2003–2011) 6.6 (2.9) 198 136 Slight (2.5)
  Cochrane 6 2007 (2006–2011) 9.3 (1.8) 29 29 (21%)  
  Non-Cochrane 13 2008 (2003–2010) 5.4 (2.4) 169 130 (96%)  
 Procedural sedation 13 2009 (2004–2013) 3.7 (1.8) 180 85 Moderate (9.3)
  Cochrane 0 NA NA NA NA  
  Non-Cochrane 13 2009 (2004–2013) 3.7 (1.8) 180 85 (100%)  
All overviews
 Total 88 2008 (1989–2013) 7.0 (2.8) 1072 608 NA
  Cochrane 30 2010 (2002–2013) 9.6 (1.6) 336 322 (53%)  
  Non-Cochrane 58 2007 (1989–2013) 5.7 (2.3) 736 469 (77%)  
  1. CCA corrected covered area, NA not applicable, SR systematic review
  2. aFor Cochrane SRs we used the year last assessed as up-to-date
  3. bEach primary study was counted only once, regardless of how many SRs included that study
  4. cCategorized using published criteria as “slight” (0–5), “moderate” (6–10), “high” (11–15), or “very high” (> 15)